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th400 leaking at front pan area, not gasket? pic inside

9K views 14 replies 9 participants last post by  nighttrain350 
#1 ·
i got this core from a freind and had it rebuilt by my trans guy that has done 7 before this. the core came with the bell but off already and from a running car. i bought a new bell and had the trans completely gone through. i noticed a leak under the car and took a look. it looks like its leaking from above the pan rail. its bone dry on the pump where the seal from teh convertor is so i know its not that. if its not that seal and not the trans pan gasket what else could be leaking? i used a can of brake cleaner on it yesterday and dried it all off. came out today from it just sitting and its back to leaking and i never even started the car. here is a pic
 
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#7 ·
The early JW bells had no small oring between each bolt hole and the pump. If you didn't use some RTV around each bolt hole between bell and pump, and some around each bolt washer it'd leak like a sieve. JW rectified the issue by counterboring for orings; they always updated older bells at recert time. Even at that, I always use some RTV on every JW bell build I do just to be safe. Check and make sure that's not the leak source. Also, the bell MUST seat flush onto the pump surface. On the TH400 case there are some "tabs" around the pump bore area that must be machined down or else the bell won't sit in place and will leak for sure.
 
#8 ·
double check that the ultra bell does not contact the pump or case any where other than the machined area it is intended for.

sometimes you may have to turn/machine the front of the pump or create some additional clearance on the case.

the bell housing bolts (to the pump) need to be sealed also. i normally leave the o-rings out and put a circle of rtv about 1/8" high around the bolt holes before i put the bell on (between the bell and the pump).

and some loctite on the bolt threads is also a good idea.
 
#12 ·
i see where you are coming from. i do that to keep the bolts tight. not to stop leaks. i have had them come loose before without it. but never with it. so i make it a practice to loctite them every time an ultra bell is installed. the rtv seals them up nicely. and when they come in for winter look over i clean and chase the threads. if they are worn i put time-serts in. that's been working good for me.
 
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